Lift tables are presently commonly used in many industries for placing various components and other items on the table surface and selectively automatically raising and lowering the table and components to a desired height. Typically, the lift tables include a base, a table top and a raising and lowering mechanism therebetween. The raising and lowering mechanism can be vertically situated hydraulic cylinders, scissor arms actuated by hydraulic cylinders, screw mechanisms etc. The mechanisms are controlled by the operator either near or remotely from the lift table.
The table and components that may be carried thereon are typically quite heavy and as a consequence, while the table is being lowered, it is possible for something that may be in the table's travel path to be damaged. It is also possible for the operator to be injured if, for example, his leg or toes are accidentally within the table traveling path. In this regard, and so as to prevent such damage and injuries from occurring, obstruction sensing guards commonly known as toe guards have been incorporated with lift tables. These guards are typically located near and below the perimeter of the table and are adapted to interrupt further movement of the table in the event that the sensor guard experiences an obstruction. One such type of sensing guard includes a sensor bar underneath and generally along the perimeter of the table and the sensor bar is hung on the table via bolts or other sliding means extending through a bore. This allows vertical movement of the sensor bar in the event of an obstruction. An electrical switch is provided between the sensor bar and the table so that upon vertical movement of the sensor bar, the switch is tripped for providing the necessary signal to the control circuit causing the table to stop from moving further. However, if the sensor guard is also exposed to a horizontal force, it is possible for the bolts or other sliding mechanism to bind within the bores preventing movement of the guard vertically upwardly and also preventing tripping of the contact switch.
In addition to the foregoing drawback, prior obstruction sensing guards are relatively time-consuming and expensive to manufacture. For example, the sensor bar as currently manufactured requires assembly by welding the various elongate lengths together around the table and thereafter lifting the toe guard and hanging the same in place via the bolts and bore configuration. As can be appreciated, this welding process requires substantial expertise and experience and, as a consequence, increases the overall cost of manufacturing.
Accordingly, a need exists for an obstruction sensing guard for vertically moving tables that will not bind in the event that both vertical and horizontal forces are experienced and which is generally easy and inexpensive to manufacture.